U.S. patent application number 15/304912 was filed with the patent office on 2017-06-22 for optical node device, optical network controller, and optical network control method.
This patent application is currently assigned to NEC Corporation. The applicant listed for this patent is NEC Corporation. Invention is credited to Shinsuke FUJISAWA, Tomoyuki HINO, Akio TAJIMA, Hitoshi TAKESHITA.
Application Number | 20170180073 15/304912 |
Document ID | / |
Family ID | 54332053 |
Filed Date | 2017-06-22 |
United States Patent
Application |
20170180073 |
Kind Code |
A1 |
TAKESHITA; Hitoshi ; et
al. |
June 22, 2017 |
OPTICAL NODE DEVICE, OPTICAL NETWORK CONTROLLER, AND OPTICAL
NETWORK CONTROL METHOD
Abstract
In an optical network based on a dense wavelength division
multiplexing system using a flexible frequency grid, it is
difficult to improve the usage efficiency of an optical frequency
band owing to the occurrence of fragmentation of the optical
frequency band; therefore, an optical network controller according
to an exemplary aspect of the present invention includes an optical
frequency region setting means for dividing an optical frequency
band used in an optical network based on a dense wavelength
division multiplexing system using a flexible frequency grid, and
setting a plurality of optical frequency regions; and an optical
path setting means for setting optical paths having a common
attribute in at least one of the plurality of optical frequency
regions.
Inventors: |
TAKESHITA; Hitoshi; (Tokyo,
JP) ; FUJISAWA; Shinsuke; (Tokyo, JP) ; HINO;
Tomoyuki; (Tokyo, JP) ; TAJIMA; Akio; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NEC Corporation |
Minato-ku, Tokyo |
|
JP |
|
|
Assignee: |
NEC Corporation
Minato-ku, Tokyo
JP
|
Family ID: |
54332053 |
Appl. No.: |
15/304912 |
Filed: |
April 15, 2015 |
PCT Filed: |
April 15, 2015 |
PCT NO: |
PCT/JP2015/002074 |
371 Date: |
October 18, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04J 14/0224 20130101;
H04J 14/026 20130101; H04J 14/02 20130101; H04B 10/27 20130101 |
International
Class: |
H04J 14/02 20060101
H04J014/02; H04B 10/27 20060101 H04B010/27 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 24, 2014 |
JP |
2014-089695 |
Claims
1. An optical network controller, comprising: an optical frequency
region setting unit configured to divide an optical frequency band
used in an optical network based on a dense wavelength division
multiplexing system using a flexible frequency grid, and set a
plurality of optical frequency regions; and an optical path setting
unit configured to set optical paths having a common attribute in
at least one of the plurality of optical frequency regions.
2. The optical network controller according to claim 1, wherein the
optical path setting unit sets each of the optical paths having an
attribute different from one another in each of the plurality of
optical frequency regions.
3. The optical network controller according to claim 1, wherein the
optical path setting unit sets the optical paths using number of
frequency slots composing each of the optical paths as the
attribute.
4. The optical network controller according to claim 3, wherein the
optical path setting unit derives the number of frequency slots
from a sum of bandwidths of an electrical signal to generate an
optical signal to be accommodated in each of the optical paths.
5. The optical network controller according to claim 1, wherein the
optical path setting unit sets the optical paths using a connection
period of the optical paths as the attribute.
6. An optical node device, comprising: an optical transmitting and
receiving unit configured to transmit and receive an optical signal
propagating through an optical network based on a dense wavelength
division multiplexing system using a flexible frequency grid; and a
control unit configured to set a center frequency and a bandwidth
of the optical signal in the optical transmitting and receiving
unit so as to accommodate the optical signal in a specific optical
path, wherein the control unit selects the specific optical path
from among optical paths having a common attribute that are set in
at least one of a plurality of optical frequency regions obtained
by dividing an optical frequency band used in the optical
network.
7. The optical node device according to claim 6, wherein the
optical paths have in common number of frequency slots composing
each of the optical paths.
8. The optical node device according to claim 6, wherein the
optical paths have a connection period of each of the optical paths
in common.
9. An optical network system, comprising: the optical network
controller according to claim 1; and an optical node device
configured to be used for an optical network based on a dense
wavelength division multiplexing system using a flexible frequency
grid; wherein the optical node device includes an optical
transmitting and receiving unit configured to transmit and receive
an optical signal propagating through the optical network, and a
control unit configured to set a center frequency and a bandwidth
of the optical signal in the optical transmitting and receiving
unit so as to accommodate the optical signal in a specific optical
path, wherein the control unit selects the specific optical path
from among optical paths having a common attribute that are set in
at least one of the plurality of optical frequency regions obtained
by dividing the optical frequency band used in the optical
network.
10. An optical network control method, comprising: dividing an
optical frequency band used in an optical network based on a dense
wavelength division multiplexing system using a flexible frequency
grid, and setting a plurality of optical frequency regions; and
setting optical paths having a common attribute in at least one of
the plurality of optical frequency regions.
11. The optical network control method according to claim 10,
wherein the setting of the optical paths includes setting each of
the optical paths having an attribute different from one another in
each of the plurality of optical frequency regions.
12. The optical network control method according to claim 10,
wherein the setting of the optical paths includes setting the
optical paths using number of frequency slots composing each of the
optical paths as the attribute.
13. The optical network control method according to claim 12,
wherein the setting of the optical paths includes deriving the
number of frequency slots from a sum of bandwidths of an electrical
signal to generate an optical signal to be accommodated in each of
the optical paths.
14. The optical network control method according to claim 10,
wherein the setting of the optical paths includes setting the
optical paths using a connection period of the optical paths as the
attribute.
15. The optical network controller according to claim 2, wherein
the optical path setting unit sets the optical paths using number
of frequency slots composing each of the optical paths as the
attribute.
16. The optical network controller according to claim 2, wherein
the optical path setting unit sets the optical paths using a
connection period of the optical paths as the attribute.
17. The optical network control method according to claim 11,
wherein the setting of the optical paths includes setting the
optical paths using number of frequency slots composing each of the
optical paths as the attribute.
18. The optical network control method according to claim 11,
wherein the setting of the optical paths includes setting the
optical paths using a connection period of the optical paths as the
attribute.
Description
TECHNICAL FIELD
[0001] The present invention relates to optical node devices,
optical network controllers, and optical network control methods,
in particular, to an optical node device, an optical network
controller, and an optical network control method that are used in
an optical network based on a dense wavelength division
multiplexing system using a flexible frequency grid.
BACKGROUND ART
[0002] A current challenge for optical communications is to expand
the capacities of optical backbone network to cope with the
possible future explosive expansion of information communications
traffic. Various approaches are being taken to the challenge. One
of the approaches is to carry out research and development
regarding an improvement in usage efficiency of an optical
frequency band.
[0003] In optical networks, optical frequency bands are used in
accordance with the Dense Wavelength Division Multiplexing (DWDM)
system standardized by the Telecommunication Standardization sector
of the International Telecommunication Union (ITU-T). In the DWDM
system, the entire available optical frequency band is divided into
narrow segments by a grid with constant width, called a wavelength
grid, and optical signals in one wavelength channel are allocated
within a grid spacing (ITU-T recommendation G.694.1).
[0004] In a flexible frequency grid that is standardized by ITU-T
recommendation G.694.1, the minimum channel spacing is set at 12.5
GHz instead of 50 GHz used conventionally, and a frequency slot
width is variable by 12.5 GHz. This makes it possible to allocate a
frequency slot of different widths to each optical path;
accordingly, it becomes possible to minimize an optical bandwidth
to be allocated to an optical path.
[0005] That is to say, the flexible frequency grid enables to
allocate an optical bandwidth only as needed. Specifically, for
example, it is only necessary in the flexible frequency grid to
allocate an optical bandwidth of 12.5 GHz if the required optical
bandwidth is equal to 12.5 GHz and to allocate an optical bandwidth
of 50 GHz if it is equal to 50 GHz. In contrast, in a fixed grid
before the introduction of the flexible frequency grid, if the
frequency slot width is set at 50 GHz, an optical bandwidth of 50
GHz is allocated equally to each optical path regardless of a
required optical bandwidth. Even though a required optical
bandwidth is 12.5 GHz, for example, the optical bandwidth to be
allocated is 50 GHz; accordingly, a bandwidth by 37.5 GHz is
allocated in vain. In contrast, the flexible frequency grid makes
it possible to reduce such unnecessary allocation of the bandwidth,
so it enables the optical frequency band usage efficiency to
improve.
[0006] However, even though the flexible frequency grid is used, an
unused frequency region can arise, and a fragmentation of the
optical bandwidth allocation may arise. It is considered that an
optical path with four slots in width is intended to be generated
and there are ten empty slots as a whole in the optical frequency
band of an optical fiber, for example. If the ten empty slots are
composed of five pairs of empty slots each of which includes two
consecutive slots, it is impossible to generate an optical path
with four slots in width. That is to say, despite the fact that
there are sufficient empty slots in total, it is impossible to
secure consecutive empty slots because the respective empty slots
are disposed in fragments. As a result, the situation may occur
where it is impossible to allocate to an optical path a wide
optical bandwidth with which high-capacity or long-distance
communications can be achieved. This is called a fragmentation of
an optical frequency, which is made easier to arise as the center
optical frequency of the optical path or the number of slots of the
optical bandwidth is changed more repeatedly.
[0007] Patent Literature 1 discloses a technology to solve the
above-mentioned problem that the fragmentation of the optical
frequency arises.
[0008] In a method for eliminating the fragmentation of an optical
spectrum in an optical network described in Patent Literature 1,
first, optical signals are allocated to a plurality of frequency
slots. This allocation is performed based on a first-fit algorithm
of searching first unoccupied consecutive frequency slots closest
to a selected frequency slot. In this case, a frequency slot
dependency map is created based on the allocation of a plurality of
optical signals to a plurality of frequency slots. The frequency
slot dependency map relates groups including one or more frequency
slots allocated to different optical signals interdependently.
[0009] If an optical signal departure event that an optical signal
is dropped from an optical network occurs, a frequency slot
occupied by the optical signal is released as a result. The optical
signal departure event and the release of frequency slots cause
fragmentation of the optical spectrum of the optical network.
[0010] In the method for eliminating fragmentation of optical
spectrum described in Patent Literature 1, the fragmentation of the
optical spectrum is eliminated by reallocating optical signals to
different frequency slots based on the frequency slot dependency
map. That is to say, by using the frequency slot dependency map
after an optical signal departure event, frequency slots of one or
more optical signals depending on a frequency slot of a dropped
optical signal are determined. Based on that information, an
optical signal is reallocated to a frequency slot released by the
departure of the dropped optical signal (defragmentation).
[0011] There are related technologies described in Patent
Literature 2 and Patent Literature 3.
CITATION LIST
Patent Literature
[0012] [PTL 1] Japanese Patent Application Laid-open Publication
No. 2013-223245 (paragraphs [0021] to [0048]) [0013] [PTL 2]
Japanese Patent Application Laid-open Publication No. H06-252867
[0014] [PTL 3] Japanese Patent Application Laid-open Publication
No. 2008-227556
SUMMARY OF INVENTION
Technical Problem
[0015] In the above-mentioned method for eliminating fragmentation
of optical spectrum described in Patent Literature 1, the
fragmentation of the optical spectrum is eliminated by reallocating
optical signals to different frequency slots based on the frequency
slot dependency map (defragmentation). However, it is difficult to
perform the defragmentation of the optical frequency band with all
the optical signals uninterrupted instantaneously. The reason is as
follows.
[0016] It is necessary to change an optical frequency of an optical
signal in an optical transmitter and receiver in order to perform
the defragmentation of an optical frequency band. However, it takes
a time from several seconds to several tens of seconds in the
present circumstances to change the optical frequency, to stabilize
the optical frequency, and to enable the optical transmitter and
receiver to launch its service.
[0017] If the defragmentation of the optical frequency band is
performed, therefore, communication services are suspended in the
intervening period. Since the interruption in communication
services takes away from user's convenience remarkably, it is
difficult to perform the defragmentation of the optical frequency
band with the interruption of communication services during
operations of the communication services. As a result, it is
impossible to resolve the fragmentation of the optical frequency
band; therefore, it is difficult to improve the usage efficiency of
the optical frequency band.
[0018] As mentioned above, there has been a problem that, in an
optical network based on a dense wavelength division multiplexing
system using a flexible frequency grid, it is difficult to improve
the usage efficiency of an optical frequency band owing to the
occurrence of fragmentation of the optical frequency band.
[0019] The object of the present invention is to provide an optical
node device, an optical network controller, and an optical network
control method to solve the problem mentioned above.
Solution to Problem
[0020] An optical network controller according to an exemplary
aspect of the present invention includes an optical frequency
region setting means for dividing an optical frequency band used in
an optical network based on a dense wavelength division
multiplexing system using a flexible frequency grid, and setting a
plurality of optical frequency regions; and an optical path setting
means for setting optical paths having a common attribute in at
least one of the plurality of optical frequency regions.
[0021] An optical node device according to an exemplary aspect of
the present invention includes an optical transmitting and
receiving means for transmitting and receiving an optical signal
propagating through an optical network based on a dense wavelength
division multiplexing system using a flexible frequency grid; and a
control means for setting a center frequency and a bandwidth of the
optical signal in the optical transmitting and receiving means so
as to accommodate the optical signal in a specific optical path,
wherein the control means selects the specific optical path from
among optical paths having a common attribute that are set in at
least one of a plurality of optical frequency regions obtained by
dividing an optical frequency band used in the optical network.
[0022] An optical network system according to an exemplary aspect
of the present invention includes an optical node device configured
to be used for an optical network based on a dense wavelength
division multiplexing system using a flexible frequency grid; and
an optical network controller, wherein the optical network
controller includes an optical frequency region setting means for
dividing an optical frequency band used in the optical network and
setting a plurality of optical frequency regions, and an optical
path setting means for setting optical paths having a common
attribute in at least one of the plurality of optical frequency
regions, the optical node device includes an optical transmitting
and receiving means for transmitting and receiving an optical
signal propagating through the optical network, and a control means
for setting a center frequency and a bandwidth of the optical
signal in the optical transmitting and receiving means so as to
accommodate the optical signal in a specific optical path, wherein
the control means selects the specific optical path from among
optical paths having a common attribute that are set in at least
one of the plurality of optical frequency regions obtained by
dividing the optical frequency band used in the optical
network.
[0023] An optical network control method according to an exemplary
aspect of the present invention includes dividing an optical
frequency band used in an optical network based on a dense
wavelength division multiplexing system using a flexible frequency
grid, and setting a plurality of optical frequency regions; and
setting optical paths having a common attribute in at least one of
the plurality of optical frequency regions.
Advantageous Effects of Invention
[0024] According to the optical node device, the optical network
controller, and the optical network control method of the present
invention, it is possible to prevent the occurrence of
fragmentation of an optical frequency band and improve the usage
efficiency of the optical frequency band in an optical network
based on a dense wavelength division multiplexing system using a
flexible frequency grid.
BRIEF DESCRIPTION OF DRAWINGS
[0025] FIG. 1 is a block diagram illustrating a configuration of an
optical network system in accordance with a first exemplary
embodiment of the present invention.
[0026] FIG. 2 is a diagram schematically illustrating optical
frequency regions to be set by an optical network controller in
accordance with the first exemplary embodiment of the present
invention.
[0027] FIG. 3 is a schematic diagram for describing an operation of
the optical network controller in accordance with the first
exemplary embodiment of the present invention.
[0028] FIG. 4 is a diagram schematically illustrating optical paths
to be initially set in optical frequency regions by the optical
network controller in accordance with the first exemplary
embodiment of the present invention.
[0029] FIG. 5 is a diagram illustrating together the numbers of
optical paths that can be set in optical frequency regions by the
optical network controller in accordance with the first exemplary
embodiment of the present invention.
[0030] FIG. 6 is a diagram schematically illustrating a usage
situation of an optical frequency band in a comparative example
with respect to the exemplary embodiments of the present
invention.
[0031] FIG. 7 is a diagram illustrating together the numbers of
optical paths that can be set in the comparative example with
respect to the exemplary embodiments of the present invention.
[0032] FIG. 8A is a schematic diagram for describing an operation
of an optical path setting means included in an optical network
controller in accordance with a second exemplary embodiment of the
present invention.
[0033] FIG. 8B is a schematic diagram for describing another
operation of the optical path setting means included in the optical
network controller in accordance with the second exemplary
embodiment of the present invention.
[0034] FIG. 8C is a schematic diagram for describing yet another
operation of the optical path setting means included in the optical
network controller in accordance with the second exemplary
embodiment of the present invention.
[0035] FIG. 9 is a schematic diagram for describing another
operation of the optical path setting means included in the optical
network controller in accordance with the second exemplary
embodiment of the present invention.
[0036] FIG. 10 is a diagram illustrating together the numbers of
optical paths that can be set in optical frequency regions by the
optical network controller in accordance with the second exemplary
embodiment of the present invention.
[0037] FIG. 11A is a table illustrating the numbers of optical
paths that can be set in optical frequency regions by the optical
network controllers in accordance with the first exemplary
embodiment and the second exemplary embodiment of the present
invention together with the case of the comparative example.
[0038] FIG. 11B is a diagram illustrating the numbers of optical
paths that can be set in optical frequency regions by the optical
network controllers in accordance with the first exemplary
embodiment and the second exemplary embodiment of the present
invention together with the case of the comparative example.
[0039] FIG. 12 is a diagram schematically illustrating optical
paths set in optical frequency regions by an optical network
controller in accordance with a third exemplary embodiment of the
present invention.
[0040] FIG. 13 is a diagram schematically illustrating a usage
situation of an optical frequency band in the optical network
controller in accordance with the third exemplary embodiment of the
present invention.
[0041] FIG. 14 is a diagram illustrating together the numbers of
optical paths set in optical frequency regions by the optical
network controller in accordance with the third exemplary
embodiment of the present invention.
[0042] FIG. 15 is a diagram schematically illustrating a usage
situation an optical frequency band in a comparative example with
respect to the third exemplary embodiment of the present
invention.
[0043] FIG. 16 is a schematic diagram for describing optical path
setting in the comparative example with respect to the third
exemplary embodiment of the present invention.
[0044] FIG. 17 is a diagram illustrating together the numbers of
optical paths that can be set in the comparative example with
respect to the third exemplary embodiment of the present
invention.
DESCRIPTION OF EMBODIMENTS
[0045] Exemplary embodiments of the present invention will be
described below with reference to the drawings.
A First Exemplary Embodiment
[0046] FIG. 1 is a block diagram illustrating a configuration of an
optical network system 1000 in accordance with a first exemplary
embodiment of the present invention.
[0047] The optical network system 1000 includes an optical network
controller 100 and an optical node device 200 that are used for an
optical network 300 based on a dense wavelength division
multiplexing system using a flexible frequency grid.
[0048] The optical network controller 100 includes an optical
frequency region setting means 110 and an optical path setting
means 120. The optical frequency region setting means 110 divides
an optical frequency band used in the optical network 300 and sets
a plurality of optical frequency regions. The optical path setting
means 120 sets optical paths having a common attribute in at least
one of the plurality of optical frequency regions.
[0049] The optical node device 200 includes an optical transmitting
and receiving means 210 and a control means 220. The optical
transmitting and receiving means 210 transmits and receives an
optical signal propagating through an optical network. The control
means 220 sets a center frequency and a bandwidth of an optical
signal in the optical transmitting and receiving means 210 so that
the optical signal may be accommodated in a specific optical path.
Here, the control means 220 selects the specific optical path from
among optical paths having a common attribute that are set in at
least one of a plurality of optical frequency regions obtained by
dividing an optical frequency band used in the optical network
300.
[0050] In the optical network system 1000 according to the present
exemplary embodiment, the optical network controller 100 is
configured to divide an optical frequency band in advance, set a
plurality of optical frequency regions, and set optical paths
having a common attribute in at least one of the plurality of
optical frequency regions. An optical network control method
according to the present exemplary embodiment includes, first,
dividing an optical frequency band used in an optical network based
on a dense wavelength division multiplexing system using a flexible
frequency grid, and setting a plurality of optical frequency
regions. And it is configured to set optical paths having a common
attribute in at least one of the plurality of optical frequency
regions.
[0051] Those configurations make it possible to prevent the
occurrence of fragmentation of an optical frequency band and
improve the usage efficiency of the optical frequency band in an
optical network.
[0052] The optical path setting means 120 can be configured to set
each optical path having an attribute different from one another in
each of a plurality of optical frequency regions.
[0053] Next, the operation of the optical network controller 100
according to the present exemplary embodiment will be described in
further detail.
[0054] A case will be described below as an example in which the
optical path setting means 120 sets optical paths using the number
of frequency slots composing an optical path as an attribute.
Specifically, as to types of optical paths, an optical path with
one slot in width, an optical path with two slots in width, and an
optical path with four slots in width are set.
[0055] In the optical network 300 illustrated in FIG. 1, "A" to "F"
represent nodes respectively. The optical node device 200 is
disposed in each node, and optical fibers connect respective nodes
to each other. Here, the optical network controller 100 is
configured to notify each optical node device 200 of optical path
setting information.
[0056] An optical fiber from the node A to the node C in the
optical network 300 will be described as an example. It is assumed
that the entirety of the optical frequency region that can be
transmitted through the optical fiber complies with a flexible
frequency grid standardized by ITU-T recommendation G.694.1, and
that the slot width of the flexible frequency grid is forty slots
wide in total. FIG. 2 illustrates the entirety of the optical
frequency region that can be transmitted through the optical fiber
from the node A to the node C. The horizontal axis represents an
optical frequency, and each rectangular block represents a
frequency slot.
[0057] The optical frequency region setting means 110 included in
the optical network controller 100 divides the optical frequency
band and sets three optical frequency regions (bands 1 to 3), for
example. A separator 1 and a separator 2 in FIG. 2 indicate an
optical frequency forming the division between the bands. In the
example illustrated in FIG. 2, the band 1 is an optical frequency
region including twelve slots, the band 2 is one including fourteen
slots, and the band 3 is one including fourteen slots.
[0058] Here, the optical path setting means 120 sets optical paths
having a common attribute in each of the optical frequency regions
(bands), respectively. Accordingly, for example, if it is
configured for the band 1 to accommodate only an optical path with
one slot in width, the band 1 cannot accommodate an optical path
with two slots in width and an optical path with four slots in
width that differ in the attribute even though there is an empty
area. FIG. 3 schematically illustrates an operation in this
case.
[0059] As illustrated in FIG. 4, eight pieces of optical path one
slot wide, five pieces of optical path two slots wide, and two
pieces of optical path four slots wide are set as initial setting
in the optical frequency regions illustrated in FIG. 2.
[0060] It is considered to set additionally, in the optical
frequency regions in the initial state illustrated in FIG. 4, new
optical paths to transmit an optical signal through the optical
fiber from the node A to the node C in the optical network 300
illustrated in FIG. 1. In this case, if it is possible to set
additionally a large number of new optical paths, the number of
empty slots, in which no optical path is set, can be decreased,
which makes it possible to increase the optical frequency usage
efficiency.
[0061] In the example illustrated in FIG. 4, the number of empty
slots is four in the band 1, four in the band 2, and six in the
band 3. In this case, the maximum number of addable optical paths
is four in the band 1 for optical path one slot wide, two in the
band 2 for optical path two slots wide, and one in the band 3 for
optical path four slots wide. These results are illustrated
together in FIG. 5.
[0062] Here, it will be considered as a comparative example to use
a flexible frequency grid without dividing an optical frequency
band by separators. In this case, there can be various usage
situations of the optical frequency band in the optical fiber
transmission line from the node A to the node C in the optical
network 300 illustrated in FIG. 1. An example of the usage
situations is illustrated in FIG. 6.
[0063] In the example illustrated in FIG. 6, the number of empty
slots is ten for empty slot one slot wide, and two for empty slot
two slots wide. In this case, two pieces of empty slot two slots
wide can be regarded as four pieces of empty slot one slot wide.
Accordingly, if each of all the empty slots is used for an optical
path one slot wide, it is possible to accommodate up to fourteen
optical paths. If maximum pieces of optical path two slots wide are
accommodated, it is possible to accommodate two pieces of optical
path two slots wide, and to accommodate ten pieces of optical path
one slot wide. These results are illustrated together in FIG.
7.
[0064] In the comparative example illustrated in FIG. 6, it is
impossible to accommodate an optical path four slots wide. However,
according to the optical network controller 100 in the present
exemplary embodiment, as illustrated in FIG. 4, it is possible to
accommodate one optical path four slots wide. This is based on the
effect that the optical network controller 100 in the present
exemplary embodiment prevents the fragmentation of the optical
frequency band from occurring in the optical fiber transmission
line from the node A to the node C in the optical network 300
illustrated in FIG. 1.
[0065] As described above, the optical network controller 100 in
the present exemplary embodiment makes it possible to accommodate
an optical path four slots wide (a large granularity optical path),
which has been impractical by the method of the comparative
example. In the present exemplary embodiment, it is unnecessary to
use the defragmentation technique as described in Patent Literature
1.
A Second Exemplary Embodiment
[0066] Next, a second exemplary embodiment of the present invention
will be described. An optical network controller according to the
present exemplary embodiment includes an optical frequency region
setting means 110 and an optical path setting means 120. The
optical frequency region setting means 110 divides an optical
frequency band used in an optical network 300 and sets a plurality
of optical frequency regions. The optical path setting means 120
sets optical paths having a common attribute in at least one of the
plurality of optical frequency regions.
[0067] The optical network controller according to the present
exemplary embodiment differs in the configuration of the optical
path setting means 120 from the optical network controller 100
according to the first exemplary embodiment. The optical path
setting means 120 in the present exemplary embodiment is configured
to derive the number of frequency slots from the sum of bandwidths
of an electrical signal to generate an optical signal to be
accommodated in an optical path. That is to say, although the
optical path setting means 120 according to the first exemplary
embodiment sets an optical path only by the multiplexing in an
optical domain, the optical path setting means 120 in the present
exemplary embodiment sets an optical path by using the multiplexing
in an electrical domain together.
[0068] For example, the optical path setting means 120 according to
the first exemplary embodiment is configured to generate an optical
path four slots wide from an electrical signal having a bandwidth
four slots wide. In contrast, the optical path setting means 120 in
the present exemplary embodiment is configured to generate an
optical path four slots wide by performing an electric-optic
conversion on an electrical signal four slots wide that is
generated by electrically multiplexing a plurality of electrical
signals, each of which has a bandwidth with a smaller slot width
than four slots width.
[0069] As illustrated in FIG. 8A, a specific example can be
configured to generate an optical path four slots wide by
performing an electric-optic conversion on an electrical signal
four slots wide that is generated by electrically multiplexing four
electrical signals, each of which has a bandwidth one slot wide.
Alternatively, as illustrated in FIG. 8B, another specific example
can be configured to generate an optical path four slots wide by
performing an electric-optic conversion on an electrical signal
four slots wide that is generated by electrically multiplexing two
electrical signals, each of which has a bandwidth two slots wide.
Alternatively, as illustrated in FIG. 8C, yet another specific
example can be configured to generate an optical path two slots
wide by performing an electric-optic conversion on an electrical
signal two slots wide that is generated by electrically
multiplexing two electrical signals, each of which has a bandwidth
one slot wide.
[0070] In generating an optical signal four slots wide, it could be
that there is only one electrical signal one slot wide and that
three pieces of electrical signal one slot wide are deficient. In
this case, an optical signal four slots wide may be generated by
adding three dummy signals or replicating the electrical signal one
slot wide. That is to say, for example, as illustrated in FIG. 9,
an optical signal (an optical path) four slots wide may be
generated by performing an electric-optic conversion on an
electrical signal four slots wide that is generated by electrically
multiplexing one electrical signal one slot wide and three pieces
of dummy electrical signal one slot wide.
[0071] However, the above-mentioned electrical multiplexing can be
applied only if all the electrical signals to be multiplexed are
transmitted from the identical node and are received by the
identical node. It is excluded to separate only a part of signals
at an intermediary node or interchange data, for example.
[0072] As mentioned above, the optical path setting means 120 in
the present exemplary embodiment is configured to use the
multiplexing in an electrical domain together. This makes it
possible to accommodate a signal one slot wide also in the band 2
and band 3 by multiplexing, whereas the signal one slot wide can be
accommodated only in the band 1 by multiplexing signals only in the
optical domain.
[0073] A specific example will be described based on the example
illustrated in the first exemplary embodiment (see FIG. 4). In the
example illustrated in FIG. 4, the number of empty slots is four in
the band 1, four in the band 2, and six in the band 3. In this
case, the maximum number of addable optical paths is four in the
band 1 for optical path one slot wide, two in the band 2 for
optical path two slots wide, and one in the band 3 for optical path
four slots wide. Using the electrical multiplexing makes it
possible to accommodate an electrical signal one slot wide in each
of all the addable optical paths. Accordingly, the maximum number
of addable optical path one slot wide is twelve in total, that is,
four in the band 1 (one slot.times.four), four in the band 2 (two
slots.times.two), and four in the band 3 (four slots.times.one).
Similarly, the maximum number of addable optical path two slots
wide is four in total, that is, zero in the band 1 because only an
optical path one slot wide can be accommodated in the band 1, two
in the band 2 (two slots.times.two), and two in the band 3 (two
slots.times.two). These results are illustrated together in FIG.
10.
[0074] If the above results are compared with the results obtained
by the optical path setting means 120 in the first exemplary
embodiment illustrated in FIG. 5, it is clear that the maximum
number of addable allocation increases in the band 1 and the band
2. This is based on the effect due to the configuration in which
the electrical multiplexing is used together. As described above,
using the electrical multiplexing together makes it possible to
improve further the usage efficiency of the optical frequency band
in the optical fiber transmission line from the node A to the node
C in the optical network 300 illustrated in FIG. 1.
[0075] If the results obtained by the optical path setting means
120 in the present exemplary embodiment illustrated in FIG. 10 are
compared with the results of the comparative example illustrated in
FIG. 7, it is clear that the maximum number of addable allocation
increases in the band 2 and the band 3. The above results are
illustrated together in FIG. 11A and FIG. 11B.
A Third Exemplary Embodiment
[0076] Next, a third exemplary embodiment of the present invention
will be described. An optical network controller according to the
present exemplary embodiment includes an optical frequency region
setting means 110 and an optical path setting means 120. The
optical frequency region setting means 110 divides an optical
frequency band used in an optical network 300 and sets a plurality
of optical frequency regions. The optical path setting means 120
sets optical paths having a common attribute in at least one of the
plurality of optical frequency regions.
[0077] The optical network controller according to the present
exemplary embodiment differs in the configuration of the optical
path setting means 120 from the optical network controller 100
according to the first exemplary embodiment. The optical path
setting means 120 in the present exemplary embodiment is configured
to use a connection period of an optical path as an attribute, and
to set optical paths having a common connection period in at least
one of the optical frequency regions. Specifically, a contract
period during which an optical path stays connected is used as the
attribute of an optical path instead of the number of slots used in
the first and second exemplary embodiments.
[0078] In general, the shorter a period during which an optical
path stays connected is, the higher the frequency of adding or
deleting an optical path is. Accordingly, the fragmentation of the
optical frequency band is made likely. The optical network
controller in the present exemplary embodiment, however, makes it
possible to prevent the occurrence of the fragmentation as will
become apparent below.
[0079] In the present exemplary embodiment, as illustrated in FIG.
12, an optical path with a connection period of one month is
accommodated in the band 1, an optical path with a connection
period of one week is accommodated in the band 2, and an optical
path with a connection period of one day is accommodated in the
band 3, for example. In the band 1 with the contract period equal
to one month, three pieces of optical path one slot wide, two
pieces of optical paths two slots wide, and one optical path four
slots wide are accommodated. In the band 2 with the contract period
equal to one week, two pieces of optical path one slot wide, one
optical path two slots wide, and two pieces of optical path four
slots wide are accommodated. In the band 3 with the contract period
equal to one day, three pieces of optical path one slot wide, and
two pieces of optical path two slots wide are accommodated.
[0080] FIG. 13 illustrates an example of the situation on a day
when one day has passed since the day that the situation of the
optical frequency region is illustrated in FIG. 12, and in the
situation, optical paths have been reconfigured in the band 3 with
the contract period equal to one day. Specifically, the situation
of the optical paths accommodated in the band 3 changes from the
situation where three pieces of optical path one slot wide and two
pieces of optical path two slots wide are accommodated to the
situation where one optical path one slot wide, one optical path
two slots wide, and two pieces of optical path four slots wide are
accommodated. FIG. 14 illustrates together changes in the number of
the optical paths allocated to the bands 1 to 3 from the first day
to the second day.
[0081] Here, it will be considered as a comparative example to use
a flexible frequency grid without dividing an optical frequency
band by separators. A usage situation of the optical frequency band
in the initial state (on the first day) in this case is assumed to
be the situation illustrated in FIG. 15, for example. In this case,
each number of optical paths having one slot, two slots, and four
slots in width is the same as that in the present exemplary
embodiment illustrated in FIG. 12.
[0082] Next, the situation on the second day is considered when a
period of one day contract has passed among the contract periods
for the optical path connection. The types of optical paths to be
added or deleted are the same as those in the present exemplary
embodiment illustrated in FIG. 13. In the case of the comparative
example, however, if trying to delete one optical path two slots
wide and two pieces of optical path one slot wide, and add one
optical path four slots wide, the number of addable optical path
four slots wide is limited to one, as illustrated in FIG. 16. FIG.
17 illustrates together increases or decreases in optical paths in
the comparative example.
[0083] As is clear from comparison of FIG. 17 with FIG. 14, the
number of addable optical path four slots wide decreases on the
second day in the comparative example. This shows that it is
possible to prevent the occurrence of fragmentation according to
the present exemplary embodiment. As a result, according to the
optical network controller in the exemplary embodiment, it is
possible to improve the usage efficiency of the optical
frequency.
[0084] The above-mentioned exemplary embodiments are described in
which the number of frequency slots composing an optical path, or a
connection period of an optical path is used as the attribute of
the optical path. The present invention, however, is not limited to
this. It is possible to use the number of domains in the optical
network through which optical paths pass, for example.
Specifically, for example, it can be considered that the entire
optical network is a group including a domain "a" of a subnetwork
controlled by the operator A, a domain "b" of a subnetwork
controlled by the operator B, and the like. In this case, an
optical path only within the domain "a", an optical path only
within the domain "b", and an optical path lying astride both in
the domain "a" and the domain "b" may be set in optical frequency
regions different from each other, respectively. A use for an
optical path, a person in charge of operating an optical path, or
the like may be used as the attribute of an optical path.
[0085] The present invention has been described by taking the
exemplary embodiments described above as model examples. However,
the present invention is not limited to the aforementioned
exemplary embodiments. The present invention can be implemented in
various modes that are apparent to those skilled in the art within
the scope of the present invention.
[0086] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2014-089695, filed on
Apr. 24, 2014, the disclosure of which is incorporated herein in
its entirety by reference.
REFERENCE SIGNS LIST
[0087] 100 Optical network controller [0088] 110 Optical frequency
region setting means [0089] 120 Optical path setting means [0090]
200 Optical node device [0091] 210 Optical transmitting and
receiving means [0092] 220 Control means [0093] 300 Optical network
[0094] 1000 Optical network system
* * * * *